# cargf, carg, cargl

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< c‎ | numeric‎ | complex

Defined in header ``<complex.h>`` |  |
float cargf( float complex z ); | (1) | (since C99)
double carg( double complex z ); | (2) | (since C99)
long double cargl( long double complex z ); | (3) | (since C99)
Defined in header ``<tgmath.h>`` |  |
#define carg( z ) | (4) | (since C99)

1-3) Computes the argument (also called phase angle) of `z`, with a branch cut along the negative real axis.
4) Type-generic macro: if `z` has type long double complex, long double imaginary, or long double, `cargl` is called. If `z` has type float complex, float imaginary, or float, `cargf` is called. If `z` has type double complex, double imaginary, double, or any integer type, `carg` is called.

### Parameters

z | - | complex argument

### Return value

If no errors occur, returns the phase angle of `z` in the interval [−π; π].

Errors and special cases are handled as if the function is implemented as atan2(cimag(z), creal(z))

### Example

Run this code

    #include <stdio.h>
    #include <complex.h>

    int main(void)
    {
        double complex z1 = 1.0+0.0*I;
        printf("phase angle of %.1f%+.1fi is %f\n", creal(z1), cimag(z1), carg(z1));

        double complex z2 = 0.0+1.0*I;
        printf("phase angle of %.1f%+.1fi is %f\n", creal(z2), cimag(z2), carg(z2));

        double complex z3 = -1.0+0.0*I;
        printf("phase angle of %.1f%+.1fi is %f\n", creal(z3), cimag(z3), carg(z3));

        double complex z4 = conj(z3); // or CMPLX(-1, -0.0)
        printf("phase angle of %.1f%+.1fi (the other side of the cut) is %f\n",
                 creal(z4), cimag(z4), carg(z4));
    }

Output:

    phase angle of 1.0+0.0i is 0.000000
    phase angle of 0.0+1.0i is 1.570796
    phase angle of -1.0+0.0i is 3.141593
    phase angle of -1.0-0.0i (the other side of the cut) is -3.141593

### References

- C11 standard (ISO/IEC 9899:2011):

  - 7.3.9.1 The carg functions (p: 196)

  - 7.25 Type-generic math <tgmath.h> (p: 373-375)

  - G.7 Type-generic math <tgmath.h> (p: 545)

- C99 standard (ISO/IEC 9899:1999):

  - 7.3.9.1 The carg functions (p: 178)

  - 7.22 Type-generic math <tgmath.h> (p: 335-337)

  - G.7 Type-generic math <tgmath.h> (p: 480)

### See also

cabscabsfcabsl (C99)(C99)(C99) | computes the magnitude of a complex number (function)
atan2atan2fatan2l (C99)(C99) | computes arc tangent, using signs to determine quadrants (function)
C++ documentation for arg

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